MSAL logging improvements

[bgavrilMS]

Discussed in https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/discussions/3010

^{Originally posted by bgavrilMS November 12, 2021}
Suggested improvements that can be made to MSAL logging:

Common log interface for MSAL/SAL/Wilson/MISE

• [Feature Request] Add new logger interface that is in alignment with SAL/Wilson/MISE #3245

Apps should not have to recompile to get verbose logs

• Allow apps to change the logging verbosity based on an env variable (this will require a process restart)
• Allow apps to change logging verbosity programmatically [Feature Request] Better align the allowed log levels of WithLogging callback with the Microsoft.Extensions.Logging #2868
• Allow apps to collect event logs, even if a logging callback has not been enabled (WithLogging + enable default logger already uses event source, but it's not turned on by default).

Better logging in token caches

• Microsoft.Identity.TokenCache should reuse MSAL's logger
• The desktop cache should reuse MSAL's logger
• Expose the correlation ID to token cache implementations [Feature Request] Provide a correlation id as part of cache callback #3008

Logging perf

• Logging should not compute log strings unless the log level is met.

Add more info in the logs

• [Feature Request] MSAL Logging should include machine info #2029
• Log important metrics irrespective of the log level Add Health/Metrics logging to MSAL that cannot be turned off. #3004

Additional discussion around logging: #1993

[bgavrilMS]

This quarter we want to do only:

• token cache logic uses MSAL loggers
• allow apps to change log level dynamically (i.e. .WithLogging(Func<LogLevel>, ...) )

[jmprieur]

@bgavrilMS dynamically? you mean on AcquireTokenXXBuilder?

[bgavrilMS]

no, I mean:

private static LogLevel _logLevel = LogLevel.Warning;

private IConfidentialClientApplicaiton CreateCCA()
{
        var cca = ConfidentialClientApplicationBuidler.Create(id).
                     .WithLogging(
                              () =>_logLevel , 
                              LogCallback);
}

// apps monitor config or env changes
private void OnConfigChange()
{
    _logLevel = // read log level from config
}

[trwalke]

updating details with #3245

[bgavrilMS]

This has not been completed.

[trwalke]

@bgavrilMS yeah, not sure how this got closed. Must a bug somewhere.

[bgavrilMS]

Tracking item for logging improvements.

[bgavrilMS]

T